The toolkit will give employers a better understanding of the physical, emotional and financial impact of a cancer diagnosis, practical guidance on how to manage employees with cancer and information on how people with cancer are protected by the Equality Act.
According to Macmillan each year, more than 100,000 people of working age are diagnosed with cancer in the UK and many of the UK's six million carers are looking after a friend or relative with cancer.
Ciarán Devane, chief executive at Macmillan Cancer Support, said: "With the number of people with cancer set to double from two to four million in the next 20 years, it's vital employers are equipped to deal with people who are working through, or after, cancer.
"Businesses would reap big rewards if people with cancer were offered effective back-to-work support. Helping people with cancer to stay in work doesn't have to be difficult and it is likely to be cheaper and easier than recruiting a replacement or defending a discrimination claim.
"We hope by using the toolkit, HR departments and managers will feel more capable and confident in supporting their employees affected by cancer. '
The toolkit includes an employer's guide produced in collaboration with CIPD, as well as posters, booklets for people with cancer and their carers and top tips for line managers.
A forum of some of Macmillan's corporate partners - nPower, Ford, New Look, Nationwide Building Society and Coventry County Council - advised Macmillan on the toolkit and the wider strategy and direction of the wider Work and Cancer Programme.
Ben Willmott, head of public policy at CIPD, added: "Supporting and managing people affected by cancer is a growing challenge for employers as more and more people who have cancer are learning to live with it as a chronic rather than a terminal illness. Their families, friends and work colleagues are also having to adapt and learn how best to support them.
"The Macmillan toolkit provides practical advice to enable employers to ensure their policies and practices are tailored to providing the necessary help to support people's recovery and enable people with cancer to remain in work, if that is what they want. It also provides guidance to help managers respond appropriately and sensitively to staff affected by cancer, including those who are carers."
The free toolkit can be ordered from Macmillan's website - www.macmillan.org.uk/work